164 THE LOWER FUNGI— PHYCOMYCETES 



function in this case is not clear. In D. achhjoides the sporangia 

 which appear first are said by Coker to free their spores as in 

 Achlya, while those which form later are typical of Dictyuchus. 

 The achlyoid condition has not been reported in other species. 



5. Brevilegnia Coker & Couch (Coker, 1927: 207). 



In addition to the type species, B. subclavata Couch (1927: 229) 

 the genus at present includes B. unisperma Coker & Braxton 

 (Coker, 1927: 213), B. unisperma var. litoralis Coker & Braxton 

 (Coker, 1927: 213), B. unisperma var. montana Coker (1927: 213) , 

 B. unisperma var. delica Coker (1927: 214), B. linearis Coker 

 (1927: 214), B. bispora Couch (1927: 228), and B. diclina Harvey 

 (1927: 245). All of these have been found only in the soil. 



As indicated in the key to genera this genus differs from 

 Thrav^totheca chiefly in that the oogonium is monosporic. The 

 sporangial stage here is essentially the same as in that genus 

 though the sporangiospores are strikingly variable in size and 

 shape. The mycelium forms a dense opaque mat; the well devel- 

 oped growth typical of water moulds having been lost, presumably 

 as a result of the changed environment. The sporangiospores 

 germinate in some cases by germ tube. In one species, B. 

 bispora, the sporangia first formed germinate as in Achlya. In 

 view of the variation which exists in the family some students 

 will prefer to widen the limits of Thraustotheca to include these 

 forms rather than to recognize this new genus. 



6. Geolegnia Coker (in Harvey 1925: 153). 



The genus contains only the two species on which it was 

 based, G. injiata Coker & Harvey and G. septisporangia Coker 

 & Harvey (Harvey, 1925: 153; 1928: 552), both isolated from 

 the soil. The mycelium forms a dense opaque mat as in the pre- 

 ceding genus. The sporangial stage is characteristic, zoospores 

 being wholly unknown. 



Very large thick-walled sporangiospores lie encysted in a 

 single row giving in early stages an aspect recalling Leptolegnia. 

 The sporangium is inflated at intervals or collapsed between 

 contiguous spores in such a manner as to appear almost monili- 

 form at maturity. The spores are freed by disintegration of 

 the sporangial wall, and germinate by tube. The oogonium is 

 monosporic, the oosphere is eccentric, and the antheridia are 

 androgynous. 



